Add -butlast

README.md

@@ -181,6 +181,7 @@ Other list functions not fit to be classified elsewhere.
 * [-last](#-last-pred-list) `(pred list)`
 * [-first-item](#-first-item-list) `(list)`
 * [-last-item](#-last-item-list) `(list)`
+* [-butlast](#-butlast-list) `(list)`
 * [-sort](#-sort-comparator-list) `(comparator list)`
 * [-list](#-list-rest-args) `(&rest args)`
 
@@ -1410,6 +1411,16 @@ Return the last item of `list`, or nil on an empty list.
 (-last-item nil) ;; => nil
 ```
 
+#### -butlast `(list)`
+
+Return a list of all items in list except for the last.
+
+```cl
+(-butlast '(1 2 3)) ;; => '(1 2)
+(-butlast '(1 2)) ;; => '(1)
+(-butlast '(1)) ;; => nil
+```
+
 #### -sort `(comparator list)`
 
 Sort `list`, stably, comparing elements using `comparator`.

dash.el

@@ -399,6 +399,14 @@ Alias: `-find'"
   "Return the last item of LIST, or nil on an empty list."
   (car (last list)))
 
+(defun -butlast (list)
+  "Return a list of all items in list except for the last."
+  (let (result)
+    (while (cdr list)
+      (!cons (car list) result)
+      (!cdr list))
+    (nreverse result)))
+
 (defmacro --count (pred list)
   "Anaphoric form of `-count'."
   (declare (debug (form form)))
@@ -1561,6 +1569,7 @@ structure such as plist or alist."
                              "--last"
                              "-first-item"
                              "-last-item"
+                             "-butlast"
                              "-count"
                              "--count"
                              "-any?"

dev/examples.el

@@ -549,6 +549,12 @@ new list."
     (-last-item '(1 2 3)) => 3
     (-last-item nil) => nil)
 
+  (defexamples -butlast
+    (-butlast '(1 2 3)) => '(1 2)
+    (-butlast '(1 2)) => '(1)
+    (-butlast '(1)) => nil
+    (-butlast nil) => nil)
+
   (defexamples -sort
     (-sort '< '(3 1 2)) => '(1 2 3)
     (-sort '> '(3 1 2)) => '(3 2 1)